It has long been considered desirable to moor smaller boats out of the water for various reasons, such as to prevent algae growth on the hull and to avoid the hazards of wave action on a boat moored at dockside.
There has heretofore been provided various hoisting structures for this purpose adapted to be placed on the bottom of a lake or other body of water, usually alongside a dock, and which are either manually operated or powered to winch a boat floated over the structure up out of the water.
For the most part, these devices have taken the form of complex and bulky rectangular frames which are expensive and do not have a trim appearance.
In U.S. Pat. No. 2,505,832 to Lange, there is disclosed a trimmer appearing hoist utilizing a set of parallel swing legs, with a power cylinder mounted horizontally to act on one of the legs. This mounting produces disadvantageous leveraging in the raised position. Further, as a result of the poor leveraging, the lifting legs are moved to a dead center condition when the boat is in the moored, hoisted position. The dead center condition may require manual shoving of the boat to initiate lowering, and the boat is less stably supported in the hoisted position so that wind and wave action may set up noisy vibrations.
Finally, the Lange structure is totally submerged when in place, making maneuvering of a boat to the proper position for hoisting difficult where viewing of the hoist is difficult because of water or lighting conditions.
Accordingly, it is an object of the present invention to provide an improved swing leg type boat hoist, in which powered movement of the swing legs is achieved with an advantageous leveraging of the power cylinders, and stable positioning of the boat in the hoisted position is accomplished allowing lowering of the boat without having to overcome a dead center condition.
Another object is to provide a submerged boat hoist in which maneuvering of the boat into proper position over the hoist to be raised is facilitated.